Picosecond transient infrared spectroscopy of electronically excited 4-dimethylamino-4'-nitrostilbene in the fingerprint region (1640-940 cm(-1))

A picosecond infrared spectrometer covering nearly the whole fingerprint region has been constructed. The infrared absorption spectrum of electronically excited (S-1 state) 4-dimethylamino-4'-nitrostilbene, which is considered to have an intramolecular charge-transfer character, has been recorded. The molar absorption coefficients of observed prominent absorption bands have been estimated to be of the order of 10(3) mol(-1) dm(3) cm(-1). Measurements of polarization dependence (pump polarization parallel/perpendicular to the probe polarization) have been performed for a few prominent bands. Assignments and polarization characteristics of the observed bands are discussed.